Deleting snapshot pages using sequence numbers and page lookups

A non-transitory machine-readable medium having instructions stored thereon which, when executed, cause the processor to:

• assign a respective monotonically-increasing sequence number (SN) to each created page of a first snapshot of a storage volume;
• assign a first snapshot sequence number (snapSN) to the first snapshot responsive to a creation of a second snapshot of the storage volume, wherein the first snapSN is equal to a largest SN of the first snapshot;
• assign a respective monotonically-increasing SN to each created page of the second snapshot, wherein a first page of the second snapshot is assigned an SN monotonically increased from the first snapSN;
• assign a second snapSN to the second snapshot responsive to a creation of a third snapshot of the storage volume in the file system, wherein the second snapSN is equal to a largest SN of the second snapshot;
• assign a respective monotonically-increasing SN to each created page of the third snapshot, wherein a first page of the third snapshot is assigned an SN monotonically increased from the second snapSN;
• and
• perform a deletion process in response to receiving a request to delete the second snapshot, wherein the deletion process includes deleting a particular page of the second snapshot responsive to determining that the particular page is not shared between the second snapshot and the first snapshot or between the second snapshot and the third snapshot.

A system, comprising:

• a first SN engine configured to assign a respective monotonically-increasing sequence number (SN) to each created page of a first snapshot of a storage volume;
• a first snapSN engine configured to assign a first snapshot sequence number (snapSN) to the first snapshot responsive to a creation of a second snapshot of the storage volume, wherein the first snapSN is equal to a largest SN of the first snapshot;
• a second SN engine configured to assign a respective monotonically-increasing SN to each created page of the second snapshot, wherein a first page of the second snapshot is assigned an SN monotonically increased from the first snapSN;
• a second snapSN engine configured to assign a second snapSN to the second snapshot responsive to a creation of a third snapshot of the storage volume in the file system, wherein the second snapSN is equal to a largest SN of the second snapshot;
• a third SN engine configured to assign a respective monotonically-increasing SN to each created page of the third snapshot, wherein a first page of the third snapshot is assigned an SN monotonically increased from the second snapSN;
• and
• a deletion engine configured to perform a deletion process in response to receiving a request to delete the second snapshot, wherein the deletion process includes deleting a particular page of the second snapshot responsive to determining that the particular page is not shared between the second snapshot and the first snapshot or between the second snapshot and the third snapshot.